This proposal requests funds for the purchase of a magnetic sector mass spectrometer, with, capabilities for doing Electron Impact Ionization (EI), Chemical Ionization (CI), Fast Atom Bombardment (FAB), and Electrospray. Our existing magnetic sector instrument is over 14 years old, and needs to be replaced. It is a heavily used service instrument that is starting to develop frequent problems due to its age. We are therefore requesting funds in order to replace it. The requested instrument is needed to support the research activities of at least 17 groups in the Chemistry Department, and at least 9 other research groups within other departments at the University. Most of these groups have substantial NIH funding. The instrument will be used for two purposes. The first purpose is obtaining full mass range, unit mass resolution spectra of organic and organometallic compounds in order to confirm identity and access purity. The second use is obtaining high resolution, exact mass measurements of molecular ions as supporting evidence of their proposed structures. These measurements are done by EI, CI, FAB, or Electrospray, depending upon which technique is most appropriate for the compound being analyzed. The versatility of a sector instrument is needed to enable all of these techniques to be used, in order to analyze the wide variety of compounds encountered. The instrument will be centrally located in the mass spectrometry service facility in the Chemistry Department. The Technical Services Committee will provide oversight and determine policies of use for the instrument The instrument will be operated, maintained, and supervised by Mr. James Windak, who has 17 years of experience operating, maintaining, and repairing magnetic sector mass spectrometers. Researchers will submit samples to be analyzed for a set fee. The funds that are generated by these fees will be used to support and maintain the instrument.